MTB helmet with a visor helps in light rain. I've never found a cycling cap with a brim that's long enough to keep the rain from dripping off the brim onto my glasses. If the rain's heavy enough, it'll clean all the grime off your glasses and give you a more-or-less uniform layer of water that's possible to see through (although if it's raining that hard, it's probably smarter to take cover until the rain passes or lightens). In between, well, you're screwed.

I wear contacts plus shades so when it's starts raining I just take off my glasses and squint.

Don't get those cheap baseball caps with the plastic mesh behind the head. Get as thin fabric as you can to wear under your helmet. The brim should protrude 3inches from your head.

I have two very thin fabric baseball caps that I got free from canoeing events.

Baseball cap under the helmet. Get one without the button thing on the top if you can. It helps a ton.

This requires somewhat upright seating otherwise the bill blocks your vision.

Baseball caps are for baseball. Why not a cycling cap for cycling?

https://www.cyclingnews.com/features/best-cycling-caps/

My favorite cycling cap says Portland, Or on the bottom of the bill, and a little logo says "ride in the rain or don't ride at all". That's where I live and that's an appropriate sentiment for the PNW.

Which is cool and all, but the larger bill of a baseball cap is better for keeping rain off glasses.

And better for impairing vision with a downward tilted head, hence cycling caps (which also tend to be of thinner material) favored by a lot of road cyclists. With tilt, cycling caps do a decent job with sun and rain.

The brims's not long enough and too rounded/tapered going to the front. It deposits the water onto your glasses. Similar to a front fender that doesn't have the mud flap that goes down close to the ground. It deposits water into your shoes. Useless.

I wonder how well the Giro helmets with the face shields work?

For places where there's lots of rain, consider a water resistant helmet cover with a brim.





Taiga helmet rain cover

IMO:

A helmet with a brim out front +
A decent wrap-around lens for your choice of glasses +
Rain-X treatment on the lenses.

It doesn't rain a tremendous amount where I live, but I've found that these steps help avoid the worst of visibility issues when it does.

I did a ride around the Olympic Peninsula (a temperate rain forest) a few weeks ago, and made the poor choice of carrying a cycling cap. Flipped up, the bill did a nice job of directing the flow of water to the corner of each eyeball. That took a while to diagnose. Flipped down, it blocked my vision without protecting my glasses. So I rode a few hundred miles with glasses off (blind beyond 200'), bill flipped down to protect the eyeballs, head tilted up and sideways so I could actually see. Next week I'll be riding from London to Edenborough and back, with rain practically guaranteed. I'll have an uncool but functional baseball cap at the ready.

Tell that to baseball players.

The one in the link shows it covering his eyes with his head upright. He won't see a thing wearing it that way with his head tilted down. And if he shifts his cap or visor up to see, his visor will be too short to keep the raindrops away.

Cycling caps are only good for the sun.

And here I was caught in a downpour just last week - I must have been fooling myself in to thinking that it helped. *shrug*

If cycling caps don't do the trick for you, that's fine, but others - including me - have found, over the course of many hours and miles, that they work well.

I use a baseball. / cycling cap with a 3” brim made of plastic not cardboard (like most caps).

I live in a high humidity area. Plenty of days where you walk out the front door and your glasses immediately fog up rain or shine. The main issue in the rain is where the moisture accumulating on the front/top of your helmet/cap exits/drips down. Whatever you decide to wear, you may have to tilt your head, move it around, etc to keep the drips from going where they don't need to.

Get a free painter's cap wherever you buy paint. See how that goes.

Daniel, good suggestion but a free painter hat has gone the way of the dodo bird. I painted a house inside and out last year and didn’t even get a can opener. I did get a stir stick. This year I painted a house is a different town with acres of deck, too, with no free swag. I will keep an eye out because I think the brim might just be the sweet spot between a bike cap and a ball cap.

Mike

Funny! This debate over brim length. Obvious (to me anyway) the optimum brim is like the optimum stem. Completely dependent on how you ride. Saying you're wrong and I'm right - pretty pointless. Right up there with Brooks saddles vs plastic shelled saddles. Drop bars vs straight bars.

Cycling cap worn under the helmet exists for a reason. Peak down and you can see in the rain, peak up and it doesn't bother you when the weather is nice. Also useful if sun is getting in your eyes.